MODIFICATIONS TO MINERAL BREAKERS

Abstract: The present invention relates to a rotor assembly for a centrifugal mineral breaker characterised in that the rotor assembly has at least one inset on the surface of either its top or bottom plate, said inset being capable of receiving either the top or bottom side of a tip assembly.

Description: MODIFICATIONS TO MINERAL BREAKERS TECHNICAL FIELD This invention relates to modifications to mineral breakers. BACKGROUND ART Reference throughout this specification shall be made to use of the present invention in relation to centrifugal mineral breakers. It should be appreciated however that the principles of the present invention could possibly apply to alternate mineral breakers or any other material or size reduction apparatus. Centrifugal mineral breakers have mineral material (such as rocks) fed axially into a rotor assembly which is revolving at high speed. Rocks are also fed into the mineral breaker so that they fall in a stream outside the rotor assembly. The rocks within the rotor assembly are flung outwardly so that they impact upon the rock stream. This impact shatters the rocks into smaller sizes. Most of the parts inside a rotor assembly are adequately protected by wear by a rock lining or wave which builds up within the rotor assembly. Those areas not protected by rock lining or wave are protected by wear parts. The surfaces located near the discharge ports of the rotor assembly are particularly vulnerable to erosion by the passage of mineral material exiting the rotor assembly. To address this problem, there are provided tip assemblies located at the discharge ports of the rotor assembly. At these ports, where it is envisaged that there will be the greatest amount of wear on the tip assembly, tungsten carbide (or any other hard material inserts are often inserted. Tungsten carbide is extremely wear resistant, but unfortunately is also very expensive and therefore it is uneconomical to have a tip completely made of this material. Thus, the material holding the tungsten carbide still wears away (along with the tungsten) and the tip assembly and tip is required to be replaced regularly. The mineral breaker can suffer serious damage if there is no tip assembly in the proximity of the discharge port. This can happen if the tip assembly wears through or breaks off due to impact or erosion wear. To avoid damage to the rotor in the event that the primary tip is worn or broken for any reason, a backup tip of similar construction may be included in the tip assembly. This backup will give some protection to the rotor assembly until the tip can be replaced. Coarse materials have typically caused premature failure of conventional tip assemblies. This is because the tip assembly is unable to resist wear and impact of the larger rocks and further unable to retain the larger sized rocks in the rock lining of the rotor. US Patent No. 4940188 discloses an attempt to address the above problem by providing an increased volume of space behind the tip assembly which allows the rock lining or wave to be more firmly held in place by the tip assembly and to hold larger rocks therein. In some cases, a large rock can overhang the tungsten and provide the wear surface itself. However, there are still problems with this configuration and a greater volume available would also be desirable. Further, in order to secure the tip assembly to the rotor assembly, it is necessary for this extra material to extend into the rock wave, thus, still taking up some volume which could be used to further retain larger rocks and secure the rock wave. This prior art assembly also only allows a single mounting system involving bolts to be utilised which again extend into the rock wave. This makes it difficult to access the bolts when it is desired to replace the tip assembly. Excessive wear also occurs at the bolt positions. Another problem experienced with conventional rotor tip assemblies for centrifugal mineral breakers is slip streaming. Slip streaming is a phenomenon which occurs when water and fine particles of dust and grit from the rocks are accelerated within the rotor and as it exits the rotor assembly. Because of the size of the particles, they find their way into various cracks, small gaps and so forth in the rotor assembly causing considerable wear to the rotor and the tip assemblies. With conventional tip assembly designs, the slip steaming would wear the ends of the tip assembly as they did not fully meet with the inside surfaces of the top and bottom rotor assembly plates. It is an object of the present invention tυ address the above problems or at least to provide the public with a useful choice. Further objects and advantages of the present invention will become apparent from the following description which is given by way of example only. DISCLOSURE OF INVENTION According to one aspect of the present invention there is provided a rotor assembly for a centrifugal mineral breaker characterised in that the rotor assembly has at least one inset on the inner surface of either its top or bottom plates, said inset being capable of receiving either the top and bottom side of a tip assembly. In preferred embodiments there are insets in both the top and bottom plates. It should be appreciated that the inner surface referred to may in some embodiments be an additional plate attached to the actual top or bottom plates of the rotor assembly. For example this plate may be a wear plate. Reference throughout this specification will be made to material in the form of rocks, grit and so forth. It should be appreciated that these terms are included merely for clarity and can be used interchangeably. As tip assemblies are required to be replaced on a regular basis, it is preferable that the insets are shaped so as to allow the easy removal of a tip assembly therefrom. Thus, in preferred embodiments the insets are substantially curved in shape allowing for easy insertion of the tip assemblies. This curvature preferably also minimises the gap between the tip and edge of the inset for the tip in any position and allows for minimum metal removal on manufacture. This invention has a number of advantages over the prior art. The rock wave which builds up within the rotor housing varies according to the type of rock, the size of the rock falling within and the configuration of the rock (say sharp or rounded). Ideally the rock wave which is built up should cover all of the vulnerable parts of the rotor assembly not protected by additional wear parts leaving only the leading edge of the tip (which is mainly tungsten carbide) exposed to the wear of the rock exiting the rotor. Thus this may be true for a certain type of rock entering into the mineral breaker set up a certain way. However, as soon as the rock type is changed, a different rock wave is formed which causes additional wear to the tip than normally encountered. The applicant has found that by adjusting the angle of the tip holder with respect to the rotor housing, the differing rock waves can be accommodated. Thus, it may be possible to adjust the angle of a tip holder prior to a different type of rock being introduced to the rotor and still accommodate the resultant differing rock wave. Ideally the angle of the tip holder shall be that the majority of wear will occur across the face of the tungsten and not the edge. The present invention can also allow for the tip assembly to be positioned at different angles with respect to the rotor assembly. For example, if a substantially curved path is provided on the inset, the tip assembly can be positioned at any portion of the curved part provided it can be secured there by some other means. According to an alternate aspect of the present invention there is provided a method of altering the angle of a tip assembly with respect to a rotor assembly of a centrifugal mineral breaker characterised by the step of providing a pivot point about which the tip assembly can rotate. It can be seen that by having a pivot point, the angle of the tip assembly can be changed which is facilitated in one embodiment by the additional step of locating the tip assembly within an inset of the rotor assembly. The means by which the tip assembly is held at the desired angle can be achieved by a variety of means. For example, the pivot may be a cog which can interact with various parts of the tip assembly, the teeth on the cog serving to hold the tip assembly into place. In preferred embodiments, there is provided a smooth pivot with a cam which operates as a stop preventing movement of the tip assembly past a pre-defined point. The force of the rocks hitting tip assemblies tend to throw the tip assemblies outwards. Because of this, it is not necessary to have stops which secure the movement of the tip assembly in two directions as the force of the rocks effectively act as a stop in one of the directions. Thus, in one embodiment, there may be provided only one stop which prevents the tip assembly from moving outwards against the force of the rocks. This can come in a variety of forms, for example a fixed wedge or block. A preferred means of providing a stop is to have an eccentric cam situated within the rotor housing. The cam may be rotatable about a pivot while capable of bearing against the base of the tip assembly (preferably the base of the tip assembly). Rotation of the cam can push the tip assembly until the tip assembly reaches the desired angle. Preferably this action is along the path set by the insets. The cam can then be locked in position such that it cannot rotate. The tip assembly may be capable of moving forwards into the rotor housing when the mineral breaker is not in operation. However, once the mineral breaker is in operation the force of the rocks exiting the rotor assembly will push the tip assembly outwards to the desired angle which in some embodiments is governed by the force of the cam against the base of the tip assembly. It should be appreciated that the present invention can apply to tip assemblies of various designs whether they have back up tips or not. The present invention has a number of advantages over the prior art. One major advantage of the present invention is that considerably less material is used than in conventional tip constructions, as there is no additional material required to extend into the rock wave to secure the tip assembly. This provides advantages in the management of the rock wave. Less material in front of the tip assembly means a greater volume of space behind the tip is available for the rock wave to be more firmly held in place and for larger rocks to be held within. This leads to less wear on the tip assembly. A further advantage of not having the attachment means extending into the rock wave is that the tip assembly can be more readily removed from the rotor assembly. Bolts are not required, which again can make it easier to detach the tip assembly from the rotor. Yet another advantage of the present invention is that the top and bottom sides of the tip assembly cannot be worn away by slip streaming as they are contained within the paths. That is, there is now no gap between the ends of the tip assembly and the rotor assembly which has been vulnerable to slip streaming. Thus it can be seen that the present invention offers a number of advantages. Firstly, there is greater volume provided to aid in the securing of the rock wave. Secondly there is provided a relatively easy means by which the angle of the tip assembly can be altered to accommodate the parameters of the rock wave. Thirdly, problems associated with slip streaming have been reduced. BRIEF DESCRIPTION OF DRAWINGS Aspects of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1: is a diagrammatic cross-sectional view of one embodiment of the present invention, and Figure 2: is a diagrammatic perspective view of the above embodiment. BEST MODES FOR CARRYING OUT TTTTC TNVENTT N With respect to Figures 1 and 2, there is illustrated means of attachment for a rotor tip assembly generally indicated by arrow 1. Only one plate 2 is shown of the rotor assembly 1, although it should be appreciated that both plates of the rotor housing will be substantially identical as regards the present invention. The plate 2 has an inset 3 which provides a substantially curved path for the tip assembly 4 to slide along. In this embodiment, the tip assembly 4 is shown to be a single tip with no back up tip, however it should be appreciated that the present invention can be used in relation to tip assemblies having other configurations. The tip assembly 4 is connected to a pivot 5 which can slot into an appropriate inset (not shown) in the rotor housing 2. An eccentric cam 6 is bolted via bolt 7 to a plate 8 within the rotor housing. Rotation of the cam 6 can be restricted or permitted by the bolt of which holds the cam 6 with respect to the rotor assembly 1. For example, rotation of the cam 6 around the bolt 7 can be achieved by loosening off the bolt 7. Likewise tightening the bolt 7 restricts rotation of the cam 6. Between the inside face of the tip assembly 4 and the cam 6 is a linkage block 9. The linkage block 9 acts to transfer force from rotation of the eccentric cam 6 to the tip assembly 4. It is envisaged that the linkage block 9 is a semi-permanent part of the rotor assembly 1 which is not replaced along with the tip assembly 4. In some embodiments the linkage block may act as a backup tip. The top arrow in Figure 1 illustrates the effect of the direction of the force that the rocks exiting the discharge port of the rotor applies to the tip assembly 4. The bottom arrow on Figure 1 illustrates the force that the cam 6 exerts against the linkage block 9 and hence the inside face of the tip assembly 4 below the pivot point 5. As the above forces are on opposing sides of the pivot, the cam 6 acts as a counter to the force of the rocks exiting the rotor assembly 1. Thus, the most outward position of the tip assembly 4 is governed by the cam 6. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the appended claims.

Claims: THE CLAIMS DEFINING TTΠ * . TNVH:NTION ARE: 1. A rotor assembly for a centrifugal mineral breaker characterised in that the rotor assembly has at least one inset on the surface of either its top or bottom plate, said inset being capable of receiving either the top or bottom side of a tip assembly. 2. A rotor assembly as claimed in claim 1 which has insets in both the bottom and top plates. 3. A rotor assembly as claimed in either claim 1 or claim 2 wherein the inset is substantially curved in shape. 4. A rotor assembly as claimed in any one of claims 1 to 3 wherein the tip assembly can be positioned at different angles with respect to the rotor assembly. 5. A tip assembly capable of being used within a rotor assembly as claimed in any one of claims 1 to 4. 6. A method of altering the angle of a tip assembly with respect to rotor assembly of a centrifugal mineral breaker characterised by the step of providing a pivot point about which the tip assembly can rotate. 7. A method as claimed in claim 6 characterised by the further step of locating the tip assembly within an inset in the rotor assembly. 8. A method as claimed in either claim 6 or claim 7 wherein the pivot is in the form of a cog. 9. A method as claimed in either claim 6 or claim 7 wherein the pivot is smooth. 10. A method as claimed in any one of claims 7 to 9 wherein there is provided a cam which operates as a stop preventing movement of the tip assembly past a pre-defined point. 11. A method as claimed in claim 10 where in the cam is eccentric. 12. A method as claimed in either claim 10 or claim 11 wherein the cam is rotatable about a pivot and capable of bearing against the tip assembly. 13. A method as claimed in any one of claims 10 to 12 wherein rotation of the cam can push the tip assembly until the tip assembly reaches a desired angle. 14. A method as claimed in any one of claims 10 to 13 wherein the cam is capable of being locked into position so that it cannot rotate. 15. A method as claimed in any one of claims 10 to 14 wherein the rotation of the cam can be restricted or permitted by a bolt holding the cam with respect to the rotor assembly. 16. A method as claimed in any one of claims 10 to 15 wherein there is provided a linkage block that acts to transfer force from rotation of the cam to the tip assembly. 17. A method as claimed in claim 16 wherein the linkage block acts as a backup tip. 18. Apparatus for performing the method as claimed in any one of claims 6 to 17. 19. A rotor assembly substantially as herein described with reference to and as illustrated by the accompanying drawings. 20. A tip assembly substantially as herein described with reference to and as illustrated by the accompanying drawings. 21. A method substantially as herein described with reference to and as illustrated by the accompanying drawings. 22. Apparatus substantially as herein described with reference to and as illustrated by the accompanying drawings.

Inventors: COLLINS TIMOTHY GEORGE, RODGER IAN GORDON, COLLINS, TIMOTHY, GEORGE, RODGER, IAN, GORDON
Applicants: COLLINS TIMOTHY GEORGE, RODGER IAN GORDON, TIDCO INT LTD, COLLINS, TIMOTHY, GEORGE, RODGER, IAN, GORDON, TIDCO INTERNATIONAL LIMITED
Application year: 1994
Main classification: B02C19
IPC codes: B02C13